Portable power hammer



Sept. 3, 1935. J, N BAKER 2,013,296

PORTABLE PQWER HAMMER dmc,

Sep. 3, 1935. 1 N BAKER 2,013,296

PORTABLE POWER HAMMER Filed July 3, 1951 4 Sheets-Sheet 2 N. BAKER2,013,296

PORTABLE POWER HAMMER Filed July 5, 1951 4 Sheets-Sheet 3 @Maw Sept. 3,1935.

Sept. 3, 1935. y 1 N. BAKER 2,013,296

PORTABLE POWER HAMMER Filed July 3, 1931 4 Sheets-Sheet 4 Patented Sept.3, 1935 UNITED ST Black & Decker Manufacturing Company,

Towson, Md., a corporation oi Maryland Application July 3, 1931, SerialNo. 548,596

14 Claims.

'Ihe present superiority in point of operation of the standard pneumaticor air hammer is due mainly to the fact that air under pressure isadmitted to the cylinder at exactly the right time V to catch the pistonas it passes Vthe dead point and force it downward with increasingvelocity until the blow is struck upon the bit or tool which may be arivet set, a metal chipping chisel or a rock drill. The increase invelocity is obtained by introduction of pressure air back of the pistonthroughout the major portion of the stroke and by the expansion of thisair.

In the most familiar type of spring operated hammer the ram is elevatedcompressing the spring by means of a cam, the ram being suddenlyreleased from the upper limit of its travel, from which point theexpansion of the spring thus released moves it to the opposite end ofits stroke. It will be understood that in a tool of this kind the energystored in the compressed spring is spent in overcoming the inertia ofthe ram, imparting thereto a certain velocity. The pressure of thespring, however, is of constantly decreasing intensity and by the timethe ram contacts the bit the full force of the spring is spent and itspressure has relaxed, and the transfer of energy to the ram has ceasedor been reduced to the minimum.

The energy transferred to the tool or bit by a ram of a given weight isdirectly proportional to the velocity of the ram at the instant the blowis struck. This velocity is, in turn, determined by the thrust appliedto the ram and the length of time during which this thrust is applied tothe ram during the working or downward stroke.

Conditions, i. e., mechanical considerations and inherent springcharacteristics, limit the stroke in a hammer of this type to theminimum length and thus limit the speed of the ram to minimum velocity.

The invention relates to a mechanical hammer so designed that the ram isgiven a double impulse, i. e., an initial velocity, by mechanical meansand an additional impulse applied at the proper instant due to therelease of the energy stored in a spring. In this way a hammer isproduced which has an increased length of effective stroke. The energyacting upon the ram is increased during Vthe rst half of the workingstroke whereupon the energy is suddenly released from a springpreviously compressed and this energy i-s added to the kinetic energyalready stored in the ram due to the speed previously generated, thusincreasing its velocity at the instant `the vblow is struck. Themechanical oper- (Cl. 12S-33) ation thus suggested gives a resultsimilar to that obtained with the air operated tool.

In the accompanying drawings I have illustrated a preferred and severalmodified forms of portable electrically operated hammer embodying themechanical features of the invention. While an electric motor is used asa source of energy in accordance with the preferred embodiment of theinvention, any suitable source of rotary energy may be substitutedtherefor.

Figure l is a fragmentary elevation partly in section showing the upperportion of a mechanical hammer embodying the invention, the sectionbeing taken on the plane of the axis.

Figure 2 is a section on the same plane of the lower portion of thehammer, the same being continuous with the lower portion of Figure 1.

Figure 3 is a transverse section on the line 3, 3 in Figure l.

Figure 4 is a longitudinal section on the axis of the barrel of amodified form of the hammer of the invention.

Figure 5 is a transverse section on the line 5, 5 in Figure 4.

Figure 6 is a longitudinal section on the line of the axis showing thebarrel of a further modilied form of the hammer of the invention.

Figure 7 is a transverse section on the line 1, I in Figure 5.

Figure 8 is a section through a block of stone or concrete showing arock drill in operation in accordance with the invention, the same beingbroken away for convenience of illustration.

Figure 9 is a section similar to Figures 4 and 6 showing still anothermodified form of the hammer in which a spring is substituted for thevacuum connection to be described.

Figure 10 is an elevation of the tool on a reduced scale.

Referring to the drawings by numerals, each of which is used to indicatethe same or similar parts in the different figures, and havingparticular reference at this time to Figures 1, 2 and 3, theconstruction shown comprises an outside casing for the hammer mechanismotherwise known as the hammer barrel I, in one end of which is located abushing or guide 2 for the tool or bit, the opposite end of the barrelbeing attached to the motor casing or frame 3 which encloses an electricmotor 1i by which the tool is driven. The casing 3 as illustrated isprovided with an extension 4 referred to herein as the crank case towhich the barrel I is directly connected by means of a flange 5. Thereis also a gear casing 6 closing the end of the motor casings and thecrank case 4 and secured thereto by flanges 1, 8. v

Within the hammer barrel I and separated therefrom by the peripheral airspace Ill), is an inner guide sleeve II, which is preferably concentricwith the barrel and in axial alignment with the tool bushing 2. Thisguide sleeve II is provided with air ports I2 at the top I4 near thecenter and as shown somewhat above the center and I5 near the bottom,and the guide sleeve as shown is supported at the top in acircumferential seat or rabbet I6 in the crank case flange I1 and at thebottom in a similar seat or rabbet i8 in the lower closed end of thebarrel or hammer casing I.

Slidably mounted in the sleeve II is a crosshead 20 having a pistonportion I9 fitting in the sleeve II and spaced lugs 2| projectingupwardly therefrom in which is mounted wristpin 22, which is engaged bythe connecting rod 24, which also engages crank pin 25 on the crank disk26, operated and supported by a short stud or crank shaft 21. This shaftis, in turn, carried and 'drivenby toothed gear 28 in the gear' casing5. This gear 28 is driven by reducing gear 29, from a pinion 3| on theshaft 32 of the motor il which also carries a centrifugal fan 33 to befurther considered. While the term crosshead is thus applied to a memberwhich resembles in function the crosshead of a steam engine, the term isused in the broad sense including any type of sliding guide member whichcan be used for the same or a similar purpose to that of cross head 20.

The ram 35 is slidably mounted in the guide sleeve I I in which it tsafter the manner of a piston in its cylinder. This ram has an upwardlydisposed reduced neck orl shaft portion 33. 'Ihe cross head 20 carries adepending tubular cage or cylinder 31 which is shown as threaded intothe cross head at 38 at its upper end extending downwardly within andpreferably concentric With the guide sleeve I I and barrel. I, andhaving'in its lower end an opening 39. This opening serves as a slidebearing for the neck or shaft 36 of the ram 35 which extends upwardlyinto the upper end of this elongated cylinder or cage 31. The upper endof the shank 36 is guided by a snug tting yet slidable piston 45, whichis removably attached to the upper end of the shaft 36 in any convenientmanner as by means of a pin 4I or a thread not shown. The cylinder 31yis thus divided by the piston il@ into two chambers 42 and 43', thevolume of which is contracted and expanded as the ram and crosshead, andhence the cylinder 31, moves up and down relatively to the barrel; Thesemembers also move one relatively to the other. The chamber 42 may bereferred to as a vacuum pot, the strength of the vacuum being regulatedby the number and size of relief ports 43 extending from the chamber 42through the cross head piston I9. The chamber 43 below the piston 55 andwithin the barrel 31 will be referred to as the compression chamber. Thecylinder 31 is provided with ports 114 in its sides covered by thepiston 4B in its lowermost position under'normal operative conditions,i. e., with a tool or' bit 45 operatively located in the tool bushing 2as shown in Figure 2.

Surrounding the cylinder 31 and bearing at its upper end on thecrosshead 23 and at its lower end on the ram 35 is a compression spring46.

When a device of this type is operated in a dust laden area the suctionproduced by the rapidly moving ram 35 has a tendency to draw dust intothe working chamber 16 immediately g below the ram and within the guidesleeve II.

This results in excessive wear and is detrimental to the operation ofthe tool. n'the operation-of this type of hammer it is avoided ashereinafter described.

It is intended to use all or part of the cooling air from the fan 33which cools the motor toy ventilate the machine and prevent theaccumulation of dust in the locations where it would do the most harm.This air is drawn into the motor casing by way of the openings 131 atthe right and after being drawn through the motor as indicated by thearrows, it is ejected downwardly by the fan 33 through the opening 48into the crank case 4 whence it passes through the opening 39 around theVconnecting rod 24 and outwardly through the ports I2 into the annularair space I5. When the ram 35 moves to its uppermost position, this airpasses through the ports I5 into the chamber L53.

The ram 35 upon its .down stroke first closes the ports I5 and thenforces Ythe air in chamber 45 outwardly and downwardly throughports 50provide-d in the lower end of the hammer barrel or casing for thispurpose or the air may be passed through a hollow drill steel, theYhollow .in the steel 45 being indicated at 5I. This manner ofdischarging the air serves to keep the cutting edge of the tool freeYfrom dust and chips as best illustrated in Figure 8, the air beingreleased adjacent the point of the tool by branch passages 52.

A small part of the air admitted through opening 49 is drawn through theports 43 into the vacuum space 42 at the upper end of the cylinder 31and from the annular space Il] .the air passes through the ports I andI5 to the inside of the sleeve II.

All of the air admitted to the hammer barrel must of necessity be cleanand free from abrasive dust. The invention therefore provides a circularair cleaning plate 5B of the centrifugal type. This is mounted on theshaft v32 Vof the motor, and in its operation it separates Ythe dustfrom the air, throwing it out of the air draft and projecting it bycentrifugal force against the wall of the motor casing 3. In this rwaythe dust is removed from the air draft and accumulates within thecasing, from whence it may be removed from time to time through anysuitable openings. Openings 41 may be utilized in this way, butpreferably other openings are provided for thisV purpose; The detailsofthis type of air cleaner, whichis well known to the art, are notimportant, and any suitable and convenient device for cleaning the airmay be substituted. l

The impact of the ram against the tool generates heat. This heatradiates to the outerk casing or hammer barrel I and would tend toincrease the temperature of this part to such va degree that discomfortto the operator would result. The passage of the air down through theannular space I!! between the barrel I and the guide stay II andoutthrough the ports 553 or the tool passage 5I serves to carry away themain portion of the heat produced by the impact aswell as the heatresulting from the movement and the friction of the reciprocating partswithin the hammer barrel. The air in the annular chamber I Il also actsas an insulator to prevent the heat from being conducted to the outershell, all o f Which provisions tend to increase the comfort to theoperator.

In the operation of the tool as the speed of the motor is increased',the speed of the crosshead 2li and. the cylinder 31 carried thereby, islikewise increased. The ram 35 is resiliently connected to the crosshead25 and the cylinder 31 by means of a sub-atmospheric pressure or vacuumin the space 42 over the piston 4i) in the cylinder 31 resulting fromthe restricted movement of the air through the passages 43, which may ormay not be valve-controlled as preferred, it being understood in thisconnection that the inertia of the ram as the speed of the pistonincreases tends to reciprocate the piston 40 in and relatively to thecylinder 31 oppositely to the motion of the crosshead which action isdampened and closely restricted by the partial Vacuum as aforesaid inthe space 42, as well as by the closed chamber 43 tending to createpressure below the piston in the chamber 43, resulting from thistendency to oppose the reciprocation. The speed and hence the momentumof the ram tend to increase as the speed of the cylinder increases butthis action is modied by the resilient as distinguished from a positiveconnection of the ram to the crosshead and cylinder 31 by means of thevacuum chamber 42 and pressure chamber 43', as aforesaid. The saidaction is also modified by the pressure of spring 43 which is opposed tothe resultant thrust on piston 40 in the chambers 42 and 43. It will befurther noted that the resilient connection or tendency of the ram tomove with cylinder 31 is reduced on each up stroke by the admission ofair through openings 43 or otherwise and its discharge on the oppositestroke.

As an illustration of the action of the ram 35, and cylinder 31, it maybe noted that the motion of the ram is arrested by and its momentum istransferred to the tool 45 at the end of the downward stroke, normallystopping the ram While ports 44 and l5 are closed. If the tool isremoved, the ram 35 is permitted to descend to a still lower position,indicated by dotted lines in Figure 2, in which event the piston 40uncovers the ports 44, thus destroying the vacuum in the chamber 42 andintroducing therein an air pressure corresponding to that in the chamber43. At the same time the pressure chamber 43' is transformed to a vacuumchamber. Under these circumstances the ram 35 may be considered asdisconnected from the oscillating cylinder 31 due to the uncovering bythe piston 40 of the ports 44 and the passage of the ram 35 by ports I5.This feature is of considerable advantage in that it obviates hammeringof the ram in idling without a tool or bit.

As soon as the tool 45 is reinserted, the ram 35 is raised thereby, theports 44 are covered by the piston 40, the excess air being forced outof the chamber 42 through the ports 43, and as the cylinder 31 descends,more air is forced out, and as the cylinder 31 ascends upon the returnstroke, a vacuum is produced in chamber 42 which resiliently ties theram 35 to the cylinder 31.

This explanation of the behavior of the ram on removal of the tool 45 isbelieved to clarify the relation of the working parts of the tool toeach other.

The tool 45 being in working position, it is understood that at slowspeeds the ram 35 is held nearly in its normal relation as shown inFigures l and 2, to the cylinder 31 by means of the spring 45, and thepartial vacuum in the chamber 42 and pressure in the chamber 43 and theram will therefore move in unison with the cylinder 31 varying therefromby a slight lag of the ram behind the crosshead and cylinder 31 due atthe beginning of the upstroke to the inertia and later to its momentum.This lag and variation increases with the speed of the crosshead. Whenworking speeds are reached, the lag of the ram behind the cylinder 31and its momentum have increased to such an extent that the pressureexerted by the spring near the, top of the upstroke is insufficient toarrest the motion of the ram until the spring is compressed andcontracted almost to the minimum and the space 42 tends to close As thecrank pin 25 passes top dead center and begins to move downwardly withincreasing Velocity, this downward motion is imparted to the cylinder31, crosshead and hence to the top of the spring 46. This added impulseto the tension already existing in the spring 45 is sufficient to'overcome the momentum of the ram and start it in the opposite direction.

The parts, i. e., the ram, the spring, the cylinder 31, the crank 26,etc. may be so proportioned that this critical point, i. e., the changeof direction of the ram, occurs at the instant the crank passes the 90position on the down stroke. Under these conditions we have the spring43 under its maximum compression when the cylinder 31 and crosshead 20are at their maximum speed on the downward or working stroke, acondition which is ideal to the delivery of the maximum impact or blowof the ram against the tool 45 and a condition which approximates thatof the air operated hammer.

Figures 6 and '1 show a construction which is identical with that shownin Figures 1, 2 and 3, except that the cylinder 51 which corresponds infunction to the cylinder 31 in Figure l, has been made integral with thecross head 58 and the piston 49, Figure 1, has been changed and theinternal annular shoulder 39 at the lower end of the cylindersurrounding the opening 3S in which the neck or rod 35 slides has beenomitted. The crosshead 58 has also been referred to herein as a powertransmitting member' or follower.

In Figure 6 the rod or neck of the ram 53 indicated by referencecharacter 59 is so proportioned as to form a close fitting piston withinthe cylinder 51, otherwise this construction is identical with thedisclosure of Figures l, 2 and 3, and the corresponding parts areindicated by the same reference characters. The only departure inprinciple of operation in the construction of Figures 6 and 7 from thatshown in Figures l, 2 and 3, is that the compression chamber 43',beneath the piston 40, and the function thereof are omitted.

The construction, Figures 4 and 5, is identical in principle ofoperation with that of Figures 6 and '7, but the actual physical contourof the parts is different in that, for the cylinder 51 in Figure 6 apiston or plunger rod 33 has been substituted, the same being formedintegrally with a cross head 6l which comprises as a part of itsintegral structure a piston 62 corresponding closely1 to theconstruction of the crosshead 23, Figure l. From the center of thepiston 62 the elongated plunger or piston 38 extends downward enteringand cooperating with a cylinder 53 formed on and integral with the ram64 from the center of which cylinder 33 projects upwardly within and forthree quarters of the length of the guide sleeve l l. This cylinder 63corresponds to the neck or shank 59 of the ram B5, Figure 6, theconstruction of Figure 6 as to these parts being thus inverted.Otherwise the structure, Figure 4 is like Figures 6 and '1. Thiscylinder 63 has ports 55 corresponding to the ports 44,

Figure 6, and ports 56 corresponding to and servingthe purpose of theports 3, Figure 6. The lower end of the ram 55 is in the form of apiston fitting and sliding in the sleeve H as the ram 35 nts and slidesin the guide sleeve Il in Figure 2, and the spring 6l bearing at one endagainst the cross head piston 62 and at the other end against the ram 64corresponds in every way to the spring 46, Figures 1 and 6.

In Figure 9, I have shown a construction which is identical with theconstruction, Figures 1, 2 and 3, except that an additional spring 'lilhas been placed in the cylinder 7i, which otherwise corresponds to thecylinder 3l, Figure 1. This spring is located in chamber 8l whichcorresponds to compression chamber 43', Figure 1. The spring 'IG bearsat one end against the piston l2, which is secured to the upper end ofthe neck or shank 'i3 of the ram 'l and has a sliding fit in thecylinder il serving the function of piston lill,

Y Figure 1, and at its lower end it bears against the annular shoulder lsurrounding the opening l at the lower end of the cylinder through whichthe shank T3 passes and in which it slides. The crosshead Ti differsfrom the crosshead 26, Figure l, in thatit is open at i9 around thewrist pin bearing l of the connecting rod 24 between the ears i8.

The operation of the two constructions, Figures 4 and V6, will obviouslybe identical each with the other and will differ from the operation ofthe construction, Figures l and 2, on account of the elimination of thecompression in chamber 43 which in normal operation assists the vacuumin the upper chamber in providing a resilient connection between thecrosshead and the ram tending to draw the ram upwardly toward thecrosshead as against its downward momentum on the down strokes and alsoas against its inertia on the upward stroke.

The construction, Figure 9, on the other hand, is similar in itsoperation to the construction, Figures 1 and 2, except that it lacks thecushioning eiiect between the crosshead and the ram, which is presentunder certain conditions of operation in the construction of Figures 1and 2 when the openings i3 are proportioned as shown. This assists thespring 46, Figures 1 and 2, in preventing impact of the piston di?against the to-p of the cylinder 3i which in the construction shown isformed by the crosshead 2li. This function is served entirely by thespring 82 in Figure 9.

I have thus described speciiically and in detail a portable power hammerin several diferent forms embodying the features of my invention, thevariation in form being intended to suggest certain variations in themanner of applying the invention and the description being specic and indetail in order that the manner of constructing, operating and using theinvention in the preferred form may be fully understood, however, thespecic terms herein are used descriptively rather than in a limitingsense, the scope of the invention being defined in the claims.

What I claim as new and desire to secure by Letters Patent is:

l. The combination in a power hammer of a reciprocating slide, a guidetherefor, a ram, a portion of said ram acting as a piston within saidslide, a spring compressed between the slide and the ram, and means forsupporting a bit in the path of the ram, a barrel enclosing the guideand spaced outwardly therefrom forming a circumferential jacket, meansfor introducing air into said jacket between the barrel and guide at onethe jacket at the upper end, the lower end of the guide cooperating withthe ram after the manner of a pump cylinder for discharging the air fromsaid jacket at the lower end of the guide.

2. The combination in a portable power hammer of a motor, a cross headoperated thereby, a guide for said crosshead, a reciprocating membercomprising a cylinder and a piston in the cylinder, a ram, one of saidmembers being connected to the ram, the other said member Vbeingconnected to the said cross head, a spring coinpressed between the ramand cross head, the cross head guide being in the form of a sleeve, abarrel enclosing the sleeve and spaced outwardly therefrom, a bit in thepath of the ram, aport for introducing air from the guide to the spacebetween the barrel and sleeve, a port for discharging air from saidspace into the path of the ram, said cross head acting as a piston toforce air from said guide into said space at the tcp, the ram serving asa piston to discharge the air from the lower end of the barrel in thevicinity of the bit, the lower end of the guide being in the form of acylinder, the ram serving to compress the air in the guide end anddischarge it in the direction of the work, the admission portr beingcovered by the piston during the discharge.

3. The combination in a power hammer of reciprocating driving means, aguide therefor, two members comprising a cylinder and a piston supportedtherein by uid pressure between the cylinder heads and piston, a ram,one said member being secured to the ram, the other said member beingsecured to the reciprocating driving means, a guide for thereciprocating driving means, a spring compressed between the said meansand the ram and a spring in said cylinder opposed to the rst mentionedspring and compressed between the piston and an opposite abutment in thecylinder.

4. The combination in a portable power hammer of a motor, a crossheadreciprocated thereby, a ram, a guide for the crosshead, a cylinder and apiston therein, one being carried by the crosshead and the other by theram, a spring compressed between the ram and the cross head, arestricted passage for venting the end of the cylinder beyond thepiston, which said end forms a vacuum and pressure chamber to transmitthe motion of the cross-head to the ram and to modify it, the cylinderalso having a port which is covered by the piston in its normal workingposition but is uncovered when the ram moves beyond the end of itsnormal working stroke.

5. The combination in a portable power hammer 0f a motor, a cross headreciprocated thereby, a guide for the cross head, a rain, two memberscomprising a cylinder and a piston in the cylinder, one said memberbeing connected tothe ram and the other to the cross head, a resilientmeans compressed between the ram and the cross head, restricted passagesfor `venting the'upper end of the cylinder, the cylinder also having aport covered by the-piston in the lower normal working position of theram, and a bit in the path of the ram, the pressure and vacuum in thecylinder, together with the spring serving to transfer the motion of thecross head to the ram and to modify the same, said. port being uncoveredat the end of the forward stroke of the ram when the hammer is operatedwith. the bit removed from the path of the ram, the ram being thuspartially released to reduce vibration.

6. The combination in a portable power ham- 'mer 0f a rotary drivingmeans, a cross head and a connecting rod, a guide for the crosshead, abarrel forming a jacket surrounding the guide, a ram within the barreloperated by the crosshead, and means for passing air through the jacketin the direction of the stroke of the ram to cool and ventilate thesame, said means including a fan driven by the rotary driving means,delivering air to one end of the jacket, the ram operating as a pistonto discharge the air from the end of the barrel or jacket in thevicinity of the bit.

'7. The combination in a portable power hammer of a rotary drivingmeans, a cross head and a connecting rod, a guide for the crosshead, abarrel forming a jacket surrounding the guide, a ram within the barreloperated by the cross head, and means for passing air through the jacketin the direction of the stroke of the ram to cool and ventilate thesame, said means including a fan driven by the rotary driving means,delivering air to one end of the barrel, the ram operating as a pistonto discharge the air from the end of the barrel in the vicinity of thebit, the air draft being mainly in contact with the outer wall of thebarrel.

8. The combination in a power hammer of a reciprocating crosshead, aguide therefor, two members comprising a cylinder and piston cooperatingto set up a iiuid pressure in theV piston, one said member being securedto the ram and the other said member to the crosshead, a guide for thecrosshead, a spring compressed between the crosshead and the ram, thesaid spring and fluid pressure serving to Vary and control the relationof the ram to the crosshead and means for supporting a tool shank in thepath of the ram.

9. The combination in a power hammer of a reciprocating crosshead, aguide therefor, two members comprising a cylinder and piston cooperatingto set up a fluid pressure in the piston, one said member being securedto the ram and the other said member to the crosshead, a guide for thecrosshead, a spring compressed between the crosshead and the ram, thesaid spring and fluid pressure serving to vary and control the relationof the ram to the crosshead and means for supporting a tool shank in thepath of the ram, the cylinder having at one end a port for the admissionof the air which is covered by the piston at the end of the workingstroke.

10. The combination in a power hammer of a reciprocating crosshead, aguide therefor, two members comprising a cylinder and piston cooperatingto set up a fluid pressure in the piston, one said member being securedto the ram and the other said member to the crosshead, a guide for thecrosshead, a spring acting on the ram to be compressed by the ram on theback stroke, the said spring and fluid pressure serving to vary andcontrol the relation of the ram to the crosshead and means forsupporting a tool shank in the path of the ram, the cylinder having atone end a port for the admission of the air which is covered by thepiston at the end of the working stroke, and a Vent for varying thepressure in said cylinder.

11. The combination in a portable power hammer of a motor, a guide, afollower reciprocated in the guide by the motor, a ram, means forretaining a bit in the path of the ram, two members comprising acylinder and a piston in said cylinder, one said member being connectedto the ram and the other to the follower, g

resilient means compressed between the ram and the follower, arestricted passage for venting the end of the cylinder beyond thepiston, which cylinder end serves as a pressure chamber to transmit themotion of the follower to the ram, the cylinder also having a port whichis covered by the piston in the normal working positions, but isuncovered when the bit is removed and the ram moves beyond its normalworking position, the ram being thus partially released to preventexcessive vibration.

12. The combination in a portable power hammer of reciprocating drivingmeans, a guide therefor, two members comprising a cylinder and a pistonin the cylinder adapted to reciprocate in said cylinder, a ram, one saidmember being connected to the ram and the other to the reciprocatingdriving means, providing a Vacuum and pressure connection between theram and driving means and a spring compressed between the reciprocatingmember and the ram, the reciprocating driving means operating in saidguide as a piston in its cylinder, said guide also acting as a guide forthe ram, a barrel enclosing the guide, the guide being spaced inwardlyfrom the barrel providing an air jacket for the guide, an air inletpassage leading to the jacket at the top and a transfer port connectingthe jacket and guide at the bottom, the reciprocating driving meansserving to introduce air at the top of said jacket and the ram servingto discharge it therefrom at the bottom.

13. The combination in a portable power hammer of reciprocating drivingmeans, a guide therefor, two members comprising a cylinder, a piston inthe cylinder adapted to reciprocate therein, a ram, one said memberbeing connected to the ram and the other to the reciprocating drivingmeans providing a connection between the driving means and the ram, saidreciprocating driving means operating in said guide as a piston in itscylinder, said guide also acting as a guide for the ram, which also hasa piston action, a barrel, the guide being spaced inwardly from thebarrel providing an air jacket for the guide and means including thedriving means operating as a piston for supplying air to the jacket atthe top, the jacket having an opening through which air is discharged atthe bottom in the path of the ram, a discharge passage leading outwardlyfrom the guide, the ram serving as a piston to draw air from the jacketand discharge it through said latter passage.

14. The combination in a power hammer of a guide, a follower in saidguide and power means for reciprocating the same, a ram in the guideconnected to the follower to be reciprocated thereby, means forsupporting a bit in the path of the ram, a barrel enclosing the guideand spaced outwardly therefrom forming a jacket, means for introducingair into said jacket at one end of the barrel, said means including thefollower operating as a piston in the guide, the lower end of the guideproviding a compression space below the ram for compressing air anddischarging the air at the lower end of the barrel, the guide havingopenings for admitting air therein from said jacket beneath the ram andfor the discharge of the air therefrom.

JAMES N. BAKER.

